Before joining Shintoho as an assistant director (under his older brother, Yoshiki Onoda), Hirata moved into still photography, and eventually joined Toho in 1953, under the studio's "New Face" program, which would lead to his casting in Godzilla (although Hirata was originally intended for the part of Ogata, eventually played by another genre regular, Akira Takarada).
When Itoi was a young boy, he accidentally viewed the wrong movie at a theater, a Shintoho film entitled Kenpei to barabara shibijin.
Following Shintoho's bankruptcy in 1961, Mihara had worked almost exclusively for Toei, including four films in Ishii's Abashiri Prison yakuza film series in 1966 and 1967 and later onsen geisha sexploitation films, eventually becoming a staple actress of the studio's "pinky violence" sub-genre by early 1970s.